This blog is intended as an occasional diary of information to feed back to hoverfly recorders in the UK and elsewhere. Inevitably there will be issues of interest that are in some way relevant to invertebrate ecologists and consequently I intend to use the medium as an opportunity to develop thoughts on pertinent topics.

Wednesday, 23 August 2017

From time-to-time participants in the UK Hoverflies Facebook
group question the value of reporting common species. Is it necessary or of any
value? My consistent response is that it is and that we do value records of
common species just as much as those of rarer species. Why might this be?

Assessing rarity for conservation status

As a starting point, we need to think about rarity - it is a
relative value. If something is rare, we need to be able to quantify it. When
the early Red Lists for the UK were compiled, a set of somewhat arbitrary values
were used to define species of conservation concern. They were based on the
numbers of 10km grid squares in which a given species was found. Broadly
speaking, anything that was known to occur in more than 15 10km squares could
not be assigned Red Data Book status. Those that occurred in 15 to 30 squares
could be listed as Notable A (now Nationally Scarce A) and from 31 to 100
squares as Notable B (Nationally Scarce B). These latter statuses are a UK
construct and are not used elsewhere.

This approach is based upon comprehensive geographic
coverage, which is really only possible for plants in the UK. It becomes much
more complicated for invertebrates, which are comparatively under-recorded. So
there is a need to use the guidelines with a modicum of expert judgment. In the
case of hoverflies, we looked at overall coverage and concluded that as the Hoverfly Recording Scheme (HRS)
has data for about 90% of 10km grid squares; setting the threshold at 90
squares for the maximum for Nationally scarce is probably about right. The
threshold may have to be reduced still further for other families of flies
where coverage is more patchy.

Assessing changes in species abundance

Species status assessment has evolved and IUCN guidance now
works on the size and vulnerability of populations. So, a species that has a
small range but a stable population is probably under less threat than a
species with a wider range that is showing signs of declining abundance. How do
we test for declining abundance when all we have is a set of maps and data that
are collected in an ad-hoc manner?

There have been a great number of attempts to develop models
that interpret such data, but the developing norm works on occupancy models
that take account of the recording effort. For these models to work effectively
we need data for both common and rarer species so that the model can test the
degree to which presence or absence is likely to be a function of biogeographic
or recording factors.

Importance in legal challenges

At a simpler scale, we need to think about the ways in which
proponents of development projects play down the importance of seemingly rare
species. It is dead easy to undermine species statuses by simply presenting
coverage maps for less well recorded taxa and emphasising the gaps. Many of those
gaps might be filled with records of commoner species that have not been
logged. So, at this very simple scale, logging common species can help to
improve general coverage and thus reinforce the importance of rarer species.

Detecting change

Conservation policy now revolves strongly around rates of
decline. There are good data for farmland birds so the declines in these
species are readily detectable and as a result the BAP process placed a lot of
emphasis on these species. Unfortunately, we know that about 40% of invertebrates
(in those taxa that can be interpreted) have also suffered similar declines.
They are not represented in Priority lists that are now enshrined in law. Why?
Well, as a starting point, birds have a very strong advocate that was able to
push away important invertebrate contenders. But, the critical issue lies in
levels of coverage and the degree to which analysis is regarded as reliable. Fewer data and more patchy coverage undermines
confidence in the analysis.

Perhaps more importantly, change is most likely to be
detected at an early stage when one looks at common species. The bigger the
dataset, the more likely change is going to be detected. So, if a species is
recorded half a dozen times each decade any fluctuation is unlikely to be
detected because a rise or fall of one individual can disproportionately alter
the statistics. Conversely, if there are hundreds or perhaps thousands of
records of another species each year, any increase or decline is likely to be
mirrored in a comparable proportion of the records received. Thus, commoner
species are actually the bellwether of change (both positive and negative).

Does it matter?

The HRS is not simply a mapping tool.
Data compiled are used in a wide variety of analyses; ranging from Species Status Reviews and the Wildlife Statistics produced by the NGOs, to analysis of
pollinator abundance by various university groups.

Until Stuart retired, the HRS data were used on a regular
basis to develop models that examine changes in both abundance and
distribution. We still get asked for access to data for similar purposes, so we
must hope that such work is ongoing. The better the data, the more likely it is
that the outputs will be believed.

Thursday, 17 August 2017

There was a bit of controversy on the
UK Hoverflies Facebook page yesterday. Debate about the ethics and/or
importance of retaining specimens led to an assertion by one
contributor that collecting for recording was an anachronism and that
it could be replaced by DNA analysis of a leg taken from a live
insect!

The concept provides rich food for
thought. Are we at that stage yet? If so, is it or will it be a
viable option?

As far as I am aware, we are a long way
off having a full database of DNA sequences for many animals and the
prospects of assembling such sequences for bigger Orders such as the
Diptera are a very long way away. There are initiatives to start the
process, but they are fraught with problems; not least that
traditional killing agents degrade DNA, so the only viable option is
to take fresh specimens and freeze them. That is relatively simple
for easily recognised species, but once one enters the realm of
difficult taxa it is likely to lead to the need to take and kill very
large numbers of individuals to track down the missing pieces. The
sheer scale of the job is immense and is not going to be achieved in
the near future. It is further complicated because the specimens must
be stored in close to pure ethanol – which is not readily available
to anyone other than registered labs.

That starts the thread of a bigger
problem

Which gene sequences are the most
useful for separating particular taxa? There has been a lot of work
on the CO1 gene in hoverflies, but this gene is not without its
limitations. I suspect there is a lot more to do before we can reliably separate some species using DNA sequencing.

BUT, I think the most worrying
complication is the degree to which identification errors are already
entering the system. Dipterists in the UK have been shocked by some
examples of gene sequencing from other parts of the World, with the
authors describing sequences for what are clearly species within a
different FAMILY let alone genus! The genie is out of the bottle and
it is going to take a fair while to put it back and then release it
under control.

What about DNA as a way of
recording?

The idea is great. You buy your
portanble gene-sequencer and catch insects that go into the sequencer
and out pops a record! What happens to the insect? I suspect early
sequencers will be fairly invasive and the animal will suffer serious
injury or death. The idea of removing a leg from a fly 3mm long
whilst keeping the animal alive is going to be dependent upon the
dexterity of the operator. I suspect there will be large numbers of
maimed and dying insects! Why not the old system of hand lens and
holding the insect in ones fingers as specialists do at the moment
for moderately doable species?

I suspect what is more likely is that
in time it will be possible to put an insect soup into a sequencer
and get a long species list of those that can be identified, plus a
tail of question marks that cannot be identified and will never be
identified because the animal has been liquidised!

What is the way forward?

There is no doubt that there is a need
for a major gene sequecing programme, and that existing specialists
will need to engage in the process. Many of us have already done so
in some capacity. It remains to be seen how fast progress is made,
but the days when there is no need for the microscope and pinned
specimens are some way off.

Critically, if DNA sequencing is to be
anything more than a dream, we need to grow a new generation of
taxonomically competent specialists. They will have to provide the technical know-how in terms of reliable species identifications to confirm what gene-sequencing tells us. Traditional taxonomists are likely to be needed for a very long way into the future! The Universities are not doing
this. I'm not sure they ever did, really. The skill of the taxonomist is the result of many years' work after graduation: getting to know their subject area in intimate detail. Such skills may once have lain in Universities, but to a large extent they were the territory of museums. Those jobs have largely gone too.

In the UK perhaps as much as 80% of the technical know-how resides in the non-vocational sector (amateurs). We must therefore make sure that taxonomic
skills survive until Nirvana is attained. The HRS is doing its bit by
running training courses and in its use of the UK Hoverflies Facebook
page to mentor new taxonomic specialists. Taxonomic expertise is at a premium and needs to be valued and nurtured if the aspiration of developing a complete DNA sequence library is ever to be achieved.

The issue of retaining specimens is one
that will never go away. Some believe that one should take nothing but
photographs and leave nothing but footprints. This mantra has existed for a couple of decades, and has become very
firmly embedded. Others, perhaps an 'old school', are more relaxed
about retaining specimens of invertebrates; and then there are the
specialist taxonomists whose experience points to a continuing need
for retaining specimens. Who is right? Or, is there a 'right' and
wrong' answer?

BWARS have produced their own policy on
specimen retention and rightly point to the need for restraint. They
also highlight the dilemma that faces the serious specialist – your
subject area is fascinating, and the animals are delightful, so why
kill them? In my case, I gave up moths many years ago because I no
longer felt that I could justify specimen retention on the grounds
that I was not adding much to science and that my collection would
not be wanted by a museum. Moreover, I was confident at the time,
that with a small number of critical exceptions I could cope with
live specimens. Thirty years on, I find I have forgotten everything
about moths and they cause me a headache! I've not got the time and
energy to go back through the learning process again!

Do we need to retain specimens at all -
Where is the evidence?

The view that photography alone will
suffice is reinforced because people can now take a photograph and
post it on one of the specialist Facebook groups or iSpot. In many
cases they will get a name, either complete or partial. Whether the
determination is correct is another matter! Unfortunately, there is
very little in the peer-reviewed literature that quantifies the
issues. I have tried to provide some basic statististics but my
patheitic attempts were met with reviewer comments ranging from 'of
little scientific importance' to 'grossly misleading and wrong'. One
reviewer ranted that at best 10% of hoverflies could be reliably
identified from photographs. I gave up trying to produce something to
fill one of the gaps!

Yet, I have good data from nearly ten
years of extracting records from photographs. Those data now
comprise perhaps as many as 100,000 records (approximately 10% of
what has been assembled by the Hoverfly Recording Scheme over 40
years). I also have a good run of personal records that have been
collected consistently over 30 years (maybe 40,000 records). So some
comparison can be made. Similarly, there are now several recorders
who are primarily photographers, but who also retain specimens that
they send to me for determination. These three models can be
compared, although scientific purists would argue that one really
needs to compare photographic data with data derived from a rigid
trapping protocol.

Are hoverflies a useful model for
evaluating the potential of photographic recording?

Hoverflies are one of those
'in-between' groups. Some are relatively straightforward to identify
from photographs, providing the photograph is of sufficient
resolution to evaluate form and markings. Even so, we occasionally
see photographs of relatively straightforward species that cannot be
firmly identified. A far greater proportion can be identified on
occasions, but unless critical features are well depicted we will
struggle to get any further than generic level. There are then the
genera that cannot be identified from photographs at all. For
example, many male Platycheirus are determined on the basis of
pits on the undersides of their feet – those are not depictable in
live animal photographs. Some species can only be done from the
internal structures within the male genital capsule (e.g.
Sphaerophoria). Others are simply fiendishly difficult without
access to comparative material (and even then cause problems).

We must also remember that we have a
typical 'island fauna' that is a sub-set of a bigger continental
fauna. Our 284 species of hoverfly compares with over 800 species in
Europe. The fauna's of our near-neighbours in The Netherlands and
Belgium are perhaps 20% bigger, even though their land area is much
smaller. It makes our job easier, but we also forget that we may well
be overlooking cryptic species amongst species that we currently
believe to be one 'easily identifiable' species. Eristalis
is one potential problem area.

What do the data tell us?

A post on this blog earlier this month
provides some indication of the sorts of differences that can be seen
when photographic data are compared with data collected by a
specialist. The most significant differences was in the relative
importance of Cheilosia in
the specialist dataset and the much higher representation of
Pipizella and Paragus
in that dataset.

The
overall message is that photography can, and does, generate a
large number of valuable records. Photographic recorders also ensure
much wider geographical coverage, and will find species that occur at
very low densities that are not well represented in the specialist
dataset. The data are, however, a sub-set of the overall fauna.

Does it matter

If
you are a naturalist who simply wants to know roughly what the animal
or plant you have seen is, then the quality of identification is not
a huge issue. It might mean that the 'lister' achieves longer or
shorter lists depending upon the level of caution used in coming to a
determination.

The
issues start when data are used for other purposes such as site
safeguard and development of species conservation strategies. If data
are skewed then it is easy for developers to undermine the confidence
that can be placed on individual records and on the conservation
status of species. This has always been a problem for invertebrates
and they are still very much a Cinderella area. To the best of my
knowledge there remain no SSSI based solely on invertebrates; yet
there probably should be. In the days of NCC and English Nature it
was an uphill battle to get invertebrates the recognition they
deserved. When BAP was developed, a huge list of birds went on as
priority species, yet invertebrates that had undergone similar levels
of decline were rejected because the data were believed not to be
reliable.

Thus,
the message has to be, if you want to see invertebrates properly
conserved, you need robust data. We just about manage this for
hoverflies, but getting similar levels of coverage and detail for,
say, fungus gnats or craneflies is impossible. Why? Because they rely
on high magnification and often upon characters that cannot be seen
in photographs. Perhaps more importantly, because there are a handful
of specialists capable of identifying them and those specialists
(wisely) will not spend their lives glued to a computer screen
identifying photographs. And, finally, not all insects are large and charismatuic. Many are minute and difficult to find.The generalist photographer will not find them and even the competent specialist may miss them unless they take a large sample. Those species make up a significant part of our fauna but will not get the recognition they deserve unless they are properly recorded.

Wednesday, 9 August 2017

When biological recording first started, its principal
objective was to map the distribution of plants and animals. Atlases became
very important and impressed a message that submitting data to a recording
scheme was about creating dots on maps. That view continues because we have
substantially failed to show what else records can be used for.

The situation is changing and Birdtrack has set the pace
with its real-time chart that shows how individual species are occurring in
comparison to previous years. This is an approach that is really only possible
when schemes get records as they are created. It depends upon high levels of
memory on the server and as such is probably beyond the options available to
smaller recording schemes. The HRS is moving in that direction as one of the
larger schemes, but as we are self-funded the costs are starting to rise and we
will need to see what we can do to cover them.

Meanwhile, Stuart is hard at work developing our new site
and including lots of nice new features that will bring us a bit closer to the
real-time Birdtrack approach. We are a little way off that format but he has
got a system working that allows analysis of previous years' data. Hopefully,
this package will be rolled out in the not too distant future, but in the
meantime here are some examples of the current state of play.

At the moment there are just short of 1 million records on
the database. I have just passed over approximately 18,000 records that we have
for 2017. Those will be incorporated into the database and the background
tables updated in the not too distant future. I've got about another week's
work sorting out other data that has been submitted in the past few months, so
I suspect the total will be nearer 25,000 when all data are assembled.

I have included maps and phenology plots for
four common and readily identifiable species to show what is possible. The maps
show that whist we have very good coverage, there are some big gaps, and plenty
of areas where the last record was made several decades ago. There is lots that
even the novice can do to help change this situation! The phenology plots are
really instructive and I think show just what the potential is for future
real-time reporting.

Note: the blue histogram represents all records (all taxa) for dates between 2001 and 2016. The subsequent graph expresses the sixteen year average phenology and the red line is the phenology for 2016 as a proportion of all records receved for the week in question. Thus the proportions for species that occur during the winter go up as the numbers of species recorded declines.

Wednesday, 2 August 2017

Over the past two years I have take a leaf out of John Bridges' book and have attempted to get out recording every day. It is a tough challenge so I reckon John does pretty well getting out as often as he does. Some months I do better than others, but in July I managed to do something every day; partly because I was walking to the hospital every day for the first 3 weeks.

My routine has been to record everything I see, no matter how common it is. If I enter a new 1km square, or new recording site unit then a new list commences. This, I hope, is not dissimilar to some of the recording by Facebook group members such as Kevin Bandage. Thus, I have attempted to create a complete record for the month that might be used for comparison with the data emerging from the Facebook group. In strictly scientific terms the comparisons are sufficiently different to say that one cannot draw firm conclusions from the data, but they do paint some important pictures.Thus, in Tables 1 & 2, I present my own data and the data extracted from the UK Hoverflies Facebook page, iSpot and Flickr for July.

Table 1. Records at generic level generated by photographic recording in July 2017. The data include a combination of full and partial records comprising a total of 5091 records.

Table 2. Records generated by RM in July 2017 comprising a total of 1758 lines of data

I have included basic counts of numbers of species and gross numbers of records aggregated at Generic level. The only point of departure between what I record and what is recorded from Photographic data is that I don't record female Sphaerophoria. In common with the photographic dataset, I created separate lines for males and females, except where the numbers reached such proportions that it was not possible to count them.

It should be noted that a substantial number of Facebook members maintain their own spreadsheets that are submitted periodically. I have not attempted to do anything with these data as this is simply a very rough analysis. More detailed analysis is needed but will require a lot more work.

The results are pretty informative.

A total of 4231 full records and 860 partial records were generated by photographic recorders. My data yielded 1757 lines for a full ID and one partial ID (a female Eumerus). When you bear in mind that most of the really assiduous recorders contributing to the HRS rarely generate more than 1,000 records in the course of a year, my efforts show what can be done but they are based on a level of effort that cannot be sustained by most recorders and would not have been sustained by me without the enforced period of hospital visiting.

It is clear that using a large pool of recorders is an extremely effective way of securing records from a wide range of species, including a significant number of relatively uncommon animals that a single recorder, no matter how diligent, is unlikely to see on a regular basis. Thus the species list for the photographic dataset stands at 101 species; whereas my own list was considerably shorter (70 species).

The same obtains at Generic level, with 50 genera reported by photographic recording as opposed to 35 by my own efforts.

Geographical coverage within the photographic dataset is country-wide, whereas my own data cover fewer than 5 hectads at locations in Northaptonshire and south London.

The ranked frequencies of the genera as represented in the two datasets (Table 3) are substantially different, as illustrated by the genus Cheilosia, which in my dataset lies second in the ranking whilst in the Photographic dataset lies at no 8. Other genera that enjoy a more prominent role in my dataset include Paragus and Pipizella. All three of these genera are difficult/impossible to do from photographs and yet are extremely abundant when recorded systematically.

The abundance of some genera such as Platycheirus in the photographic dataset suggests that there may be a weakness in my search techniques for these genera, although I am at a loss to understand why that may be so - not only do I make visual searches, I also sweep suitable vegetation wherever possible (hence the strong representation of Paragus in my data).

On this note, I suspect the answer to some of the differences in frequencies probably lies in regional variation in species' abundance. For example, I have been amazed by the numbers of Volucella inanis and V. zonaria in south London this year. Conversely, SE England is always very weak for Leucozona glaucia and L. laternaria; hence their poor showing in my data.

Table 3. Comparative positions of individual genera when organised in rank order within the two datasets.

Thus, what can we say about the data? Well, both systems have their strengths and weaknesses. I suspect that what we really need is a network of recorders who adopt similar techniques to those I employ if we are to establish the sort of contextual data we need to make full use of the photographic dataset and to understand the trends that might be conveyed in both datsets.

About Me

An ecologist with over 30 years experience in statutory nature conservation and biological recording. I am now an independent coastal management consultant (Bright Angel Coastal Consultants Ltd.) and have undertaken commissions in the UK and several northern European countries. I originally trained as an entomologist and parasitologist. Today, I retain an interest in entomology but in a strictly non-vocational capacity. In my non-working time I am joint organiser of the Hoverfly Recording Scheme (with Dr Stuart Ball) and am extremely committed to developing new capacity in insect identification and biological recording.